#include "FLOAT.h"

FLOAT F_mul_F(FLOAT a, FLOAT b) {
	long long res = (long long)a * (long long)b;
	return (FLOAT)(res >> 16);//都转化为整数除法，再进行FLOAT型转化就行
}

FLOAT F_div_F(FLOAT a, FLOAT b) {
	/* Dividing two 64-bit integers needs the support of another library
	 * `libgcc', other than newlib. It is a dirty work to port `libgcc'
	 * to NEMU. In fact, it is unnecessary to perform a "64/64" division
	 * here. A "64/32" division is enough.
	 *
	 * To perform a "64/32" division, you can use the x86 instruction
	 * `div' or `idiv' by inline assembly. We provide a template for you
	 * to prevent you from uncessary details.
	 *
	 *     asm volatile ("??? %2" : "=a"(???), "=d"(???) : "r"(???), "a"(???), "d"(???));
	 *
	 * If you want to use the template above, you should fill the "???"
	 * correctly. For more information, please read the i386 manual for
	 * division instructions, and search the Internet about "inline assembly".
	 * It is OK not to use the template above, but you should figure
	 * out another way to perform the division.
	 */
	int c = 1;
	if ((a < 0) == 1)
	{
		a = -a;
		c *= -1;
	}
	if ((b < 0) == 1)
	{
		b = -b;
		c *= -1;
	}
    //c判断最后结果的正负
	int ret = a / b;
	a %= b;

	int i;
	for (i = 0; i < 16; i++)
	{
		a = a << 1;
		ret = ret << 1;
		if (a >= b)
		{
			a -= b;
			ret = ret | 1;
		}
	}
	return c * ret;
}

FLOAT f2F(float a) {
	/* You should figure out how to convert `a' into FLOAT without
	 * introducing x87 floating point instructions. Else you can
	 * not run this code in NEMU before implementing x87 floating
	 * point instructions, which is contrary to our expectation.
	 *
	 * Hint: The bit representation of `a' is already on the
	 * stack. How do you retrieve it to another variable without
	 * performing arithmetic operations on it directly?
	 */

	int b = *(int *)&a;
	int last = b & 0x7fffff;
	int e = (b >> 23) & 0xff;
	int s = b & 0x80000000;

	if (e == 255)
	{
		if (s)
			return -0x7fffffff;
		else
			return 0x7fffffff;
	}

	if (e == 0)
	{
		return 0;
	}

	last = last | (1 << 23);
	e = e - 134;
	if (e < 0)
	{
		last = last >> (-e);
	}
	if (e > 0)
	{
		last = last << e;
	}
	if (s)
	{
		return -last;
	}
	else
	{
		return last;
	}
}

FLOAT Fabs(FLOAT a) {
	if (a < 0)
		return -a;
	else
		return a;
}

/* Functions below are already implemented */

FLOAT sqrt(FLOAT x) {
	FLOAT dt, t = int2F(2);

	do {
		dt = F_div_int((F_div_F(x, t) - t), 2);
		t += dt;
	} while(Fabs(dt) > f2F(1e-4));

	return t;
}

FLOAT pow(FLOAT x, FLOAT y) {
	/* we only compute x^0.333 */
	FLOAT t2, dt, t = int2F(2);

	do {
		t2 = F_mul_F(t, t);
		dt = (F_div_F(x, t2) - t) / 3;
		t += dt;
	} while(Fabs(dt) > f2F(1e-4));

	return t;
}
